1. Field of the Invention
This invention relates to a new, oil-soluble zinc-molybdenum-based dithiocarbamate derivative, a method of producing the same, a lubricant additive containing the same as the effective component, and a lubricant composition containing the same, more particularly a new compound having the metallic components of zinc and molybdenum in the same molecule, a method producing the same, a lubricant additive comprising the same, and a lubricant composition containing the same.
2. Prior Art
Recently, energy saving has been promoted in all industrial fields for environmental preservation. In particular, automobile engines are required to reduce friction loss in the engine, because loss of kinetic energy resulting from friction generated in the power transmission system increases fuel consumption.
Reduction in friction loss in the engine has been pursued by improving lubricants, in addition to designs of engines themselves. A number of methods have been proposed to reduce friction by, e.g., decreasing viscosity of the base oil, and use of new friction modifiers, to reduce friction in the boundary lubrication region and thereby to reduce fuel consumption.
For example, sulfurized oxymolybdenum dithiocarbamate has been proposed as a friction modifier, as disclosed by, e.g., U.S. Pat. No. 3,356,702. Compounds which have been used as oilness agent preparations, such as glycerin ester, have been also proposed as friction modifiers, as disclosed by JP Publication No. 62-54359.
However, it has been clarified that sulfurized oxymolybdenum dithiocarbamate, although decreasing friction coefficient to some extent at low temperature, suffers a decreased effect of reducing friction at high temperature seen as an increase in friction coefficient, and that it cannot exhibit the friction-reducing effect sufficiently substanably, even at low temperature, for an equipment required to operate continuously for extended periods.
It is also known that zinc dithiophosphate (ZnDTP) shows a friction-reducing effect, when incorporated in a lubricant. However, there is a requirement to reduce phosphorus content, because phosphoric acid resulting from combustion of the phosphate damages oxidation catalysts in the exhaust gas clean-up system.
Under these circumstances, development of a lubricant composition which exhibits a friction-reducing effect over a wide temperature range has been earnestly demanded, because of widely changing conditions under which an automobile engine, and hence the lubricant therefor, are used.